1. Field of the Invention
The present invention relates to a method of measuring a film thickness distribution of an organic coating film, which is suitable for use in a photolithography process corresponding to one process in a method of manufacturing a semiconductor device, and particularly to a method of measuring a film thickness distribution of an organic coating film formed over a substrate having steps.
2. Description of the Related Art
A method described in ┌Resist Material Handbook For Semiconductor Integrated Circuit (1996.7.31, REALIZE INC.) pp. 245┘ has been known as a method of measuring the thickness of an organic coating film (hereinafter called xe2x80x9corganic filmxe2x80x9d) such as a resist, which is employed in a conventional photolithography process. A tracer or needle-touching method is a method of scratching part of an organic film formed over a substrate and causing an inspection needle to scan a substrate-exposed portion before and after the exposure of the substrate, thereby measuring the thickness of the organic film. An interference type film thickness measuring method is a method of vertically launching a plurality of lights different in wavelength from one another into a single-layered organic film, measuring the intensities of reflected lights for every wavelengths and calculating the thickness of the organic film by using the known refractive indexes set every organic films. The measurement of the thickness of an organic film formed over a substrate having steps is carried out by observing a cut cross-section of the substrate through the use of Scanning Electron Microscopy (SEM).
However, the above-described conventional film-thickness measuring methods involve the following problems. The needle-touching method encounters difficulties in continuously measuring the thickness of the organic film formed over the substrate having the steps. The interference type film thickness measuring method is fit for the measurement of the thickness of the single-layered organic film but unfit for the measurement of an organic film on a substrate with a bed or base film formed thereon. Further, the observation of the cut cross-section of the substrate by SEM needs to cut the substrate. Therefore, the substrate cannot be recycled and a wafer used only for the film-thickness measurement is required, thus causing demerits in terms of cost. Since the substrate is normally cut outside a clean room, the observation of the cross-section thereof by SEM needs much time and the number of man-hours.
With the foregoing problems in view, it is therefore an object of the present invention to measure a film thickness distribution of an organic film formed over a semiconductor wafer having steps, as a continuous value without destroying the semiconductor wafer.
According to one aspect of the invention, there is provided a film thickness distribution measuring method, comprising the following steps of measuring a step form lying within a predetermined interval including a substrate exposure region having a coordinate point defined as a measurement reference on a substrate having steps to thereby extract first data L1, forming an organic film over the substrate and thereafter measuring a step form lying within the predetermined interval to thereby extract second data L2, measuring the thickness of the organic film and adding the measured thickness to the second data L2 to thereby extract third data L3, and determining a difference (L3xe2x88x92L1) between the third data L3 and the first data L1 to thereby measure a continuous film thickness distribution of the organic film formed over the substrate.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.
While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:
FIG. 1 is a plan view showing a semiconductor wafer according to the present invention;
FIGS. 2(a)-2(d) are respective diagrams for explaining film thickness distribution measurements according to a first embodiment of the present invention;
FIG. 3 is an explanatory view illustrating another example of the first embodiment of the present invention; and
FIGS. 4(a)-4(e) are respective diagrams for explaining film thickness distribution measurements according to a second embodiment of the present invention.